1. Field of the Invention
The present invention relates to a low-cost zoom lens system having a zoom ratio of approximately 5:1 for use in a compact, light-weight digital camera, and also relates to an electronic imaging apparatus which employs such a zoom lens system.
2. Description of Related Art
Due to rapid popularization of digital cameras in recent years, demands are being made for lower-cost digital cameras, and also there is a strong demand for a lower-cost photographic optical system therefor. Whereas, there is a strong demand for an increased zoom ratio in order to increase the added value of the camera, so that a zoom lens system having a zoom ratio of approximately 5:1 is demanded, even in a low-cost digital camera.
For instance, a positive-lead zoom lens system configured of four lens groups is often employed as a zoom lens system having a zoom ratio exceeding 5:1. However, although such a type of zoom lens system is suitable for achieving a high zoom ratio, since the number of lens elements is large, it is difficult to achieve a low cost and miniaturized zoom lens system.
Whereas, zoom lens systems, in the form of a negative-lead zoom lens system having three lens groups, which achieve a lowered cost by employing a large number of resin lens elements are known in the art (e.g., Japanese Unexamined Patent Publication Nos. 2007-193140, 2008-233499, 2008-233871 and 2009-092740). However, each of these publications only discloses a zoom lens system having zoom ratio of approximately 3:1, which does not sufficiently achieve a high zoom ratio.